[codex] Validate export filters before job enqueue

[kitwongpixel]

What changed

• Added synchronous export filter validation before queue insertion.
• Normalized ISO date inputs, workspace filters, and status filters before creating a job.
• Rejected invalid date ranges, blank workspace IDs, and unsupported statuses before enqueue.
• Added regression coverage for valid normalization and invalid-filter rejection.

Why

The bulk export path was allowing partially validated filters to reach worker execution. That made failures show up late and could enqueue jobs with unintended ranges.

Validation

• python3 -m py_compile src/api/routes.py src/data/exports.py tests/test_data_exports.py
• git diff --check

Closes #3421

[sivaadityacoder]

/attempt #3598

Hey! Just opened a PR that resolves this issue. I've also starred the repo for the bounty requirement!

Let me know if there's anything else you need.